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Electrical efficiency
 
 
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The efficiency of an entity (a device
Machine

A machine is any device that uses energy to perform some activity. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work....
, component
Electronic component

An electronic component is a basic Electronics element usually packaged in a discrete form with two or more connecting leads or metallic pads....
, or system
System

System is a set of interacting or interdependent entities, real or abstract, forming an integrated whole.The concept of an "integrated whole" can also be stated in terms of a system embodying a set of relationships which are differentiated from relationships of the set to other elements, and from relationships between an element of the se...
) in electronics
Electronics

Electronics refers to the flow of charge through nonmetal electrical conductor , whereas electrical refers to the flow of charge through metal electrical conductor....
 and electrical engineering
Electrical engineering

Electrical engineering, sometimes referred to as electrical and electronic engineering, is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism....
 is defined as useful power output divided by the total electrical power consumed (a fractional expression
Expression (mathematics)

In mathematics, the word expression is a term for any well-formed formula combination of mathematical symbols. For example,is an expression, while...
), typically denoted by the Greek letter small Eta.



Efficiency of typical electrical devices
Efficiency should not be confused with effectiveness
Effectiveness

Effectiveness means the capability of producing an effect.In Medicine, effectiveness relates to how well a treatment works in practice, as opposed to efficacy, which measures how well it works in clinical trials or laboratory studies....
: a system that wastes most of its input power but produces exactly what it is meant to is effective but not efficient.






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Encyclopedia


The efficiency of an entity (a device
Machine

A machine is any device that uses energy to perform some activity. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work....
, component
Electronic component

An electronic component is a basic Electronics element usually packaged in a discrete form with two or more connecting leads or metallic pads....
, or system
System

System is a set of interacting or interdependent entities, real or abstract, forming an integrated whole.The concept of an "integrated whole" can also be stated in terms of a system embodying a set of relationships which are differentiated from relationships of the set to other elements, and from relationships between an element of the se...
) in electronics
Electronics

Electronics refers to the flow of charge through nonmetal electrical conductor , whereas electrical refers to the flow of charge through metal electrical conductor....
 and electrical engineering
Electrical engineering

Electrical engineering, sometimes referred to as electrical and electronic engineering, is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism....
 is defined as useful power output divided by the total electrical power consumed (a fractional expression
Expression (mathematics)

In mathematics, the word expression is a term for any well-formed formula combination of mathematical symbols. For example,is an expression, while...
), typically denoted by the Greek letter small Eta.



Efficiency of typical electrical devices


Efficiency should not be confused with effectiveness
Effectiveness

Effectiveness means the capability of producing an effect.In Medicine, effectiveness relates to how well a treatment works in practice, as opposed to efficacy, which measures how well it works in clinical trials or laboratory studies....
: a system that wastes most of its input power but produces exactly what it is meant to is effective but not efficient. The term "efficiency" only makes sense in reference to the wanted effect. So a light bulb might have 2% efficiency at emitting light yet still be 98% efficient at heating a room. (In practice it is nearly 100% efficient at heating a room because the light energy will also be converted to heat eventually, apart from the small fraction that leaves through the windows). An electronic amplifier
Electronic amplifier

An electronic amplifier is a device for increasing the Power and/or amplitude of a Signal . It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude....
 that delivers 10 watts of power to its load (for example a loudspeaker
Loudspeaker

A loudspeaker, speaker, or speaker system is an electroacoustical transducer that converts an electricity signal processing to sound....
), while drawing 20 watts of power from a power source is 50% efficient. (10/20 × 100% = 50%)

  • Electric kettle: over 90% (comparatively little heat energy is lost during the 2 to 3 minutes a kettle takes to boil water).
  • A four-quadrant gate
    Four-quadrant gate

    A four-quadrant gate is a type of boom barrier gate protecting a grade crossing.It has a gate mechanism on both sides of the tracks for both directions of automotive traffic....
     is highly effective, yet it has an electrical efficiency close to 0%.


Efficiency of devices at point of Maximum Power Transfer


As a result of the Maximum Power Theorem
Maximum power theorem

In electrical engineering, the maximum power theorem states that, to obtain maximum external power from a source with a finite internal electrical resistance, the resistance of the load must be made the same as that of the source....
, devices transfer maximum power to a load when running at 50% electrical efficiency. This occurs when the load resistance (of the device in question) is equal to the internal Thevenin equivalent resistance of the power source.

This is incorrect. Example 4.12 from Nilsson's "Electric Circuits", 7th ed. is perfect example. In that example maximum power transfer occurs at efficiency of 35.71%.

Efficiency of light bulbs


  • Incandescent light bulb
    Incandescent light bulb

    The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric light that works by incandescence, ....
    : about 2%.
  • Compact fluorescent lamp
    Compact fluorescent lamp

    File:Energiesparlampe 01 retouched.jpgA compact fluorescent lamp , also known as a compact fluorescent light or energy saving light , is a type of fluorescent lamp....
    : about 7% to 9%.
  • White Light-emitting diode
    Light-emitting diode

    A light-emitting diode , is an electronic light source. The LED was discovered in the early 20th century, and introduced as a practical electronic component in 1962....
     (LED) about 4% to 10%.


Discussion


High efficiency is obviously desirable when we wish to design
Design

Design is used both as a noun and a verb. The term is often tied to the various applied arts and engineering . As a verb, "to design" refers to the process of originating and planning for a product, structure, system, or component with intention....
 system
System

System is a set of interacting or interdependent entities, real or abstract, forming an integrated whole.The concept of an "integrated whole" can also be stated in terms of a system embodying a set of relationships which are differentiated from relationships of the set to other elements, and from relationships between an element of the se...
s that can operate from batteries
Battery (electricity)

In electronics, a battery or voltaic cell is a combination of one or more electrochemical cell Galvanic cells which store chemical energy that can be converted into electric potential energy, creating electricity....
. Inefficiency has a cost (either paid to the power company or the cost of the required power supply
Power supply

Power supply is a reference to a source of electrical power. A device or system that supplies electrical or other types of energy to an output External electric load or group of loads is called a power supply unit or PSU....
) to be weighed against the cost of attaining greater efficiency (choosing different components or redesigning the system). Also, any difference in the input and output power probably produces heat within the system (though noise
Noise

In common use, the word noise means unwanted sound or noise pollution. In electronics noise can refer to the electronic signal corresponding to acoustic noise or the electronic signal corresponding to the noise commonly seen as 'Noise ' on a degraded television or video image....
 and other mechanical vibration
Oscillation

Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and Alternating current power....
s involve at least theoretically separate and generally negligible inefficiencies), and that heat must be removed from the system if it is to remain within its operating temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 range. If the system is in a climate controlled environment (e.g. a home or office), heat generated may reduce heating costs or increase ventilation and air conditioning costs.

See also


  • Battery
    Battery (electricity)

    In electronics, a battery or voltaic cell is a combination of one or more electrochemical cell Galvanic cells which store chemical energy that can be converted into electric potential energy, creating electricity....
  • Electronic amplifier
    Electronic amplifier

    An electronic amplifier is a device for increasing the Power and/or amplitude of a Signal . It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude....
  • List of electronics topics
    List of electronics topics

    This is a list of communications, computers, electronic circuits, fiberoptics, microelectronics, medical electronics, reliability, and semiconductors....
  • Maximum Power Theorem
    Maximum power theorem

    In electrical engineering, the maximum power theorem states that, to obtain maximum external power from a source with a finite internal electrical resistance, the resistance of the load must be made the same as that of the source....
  • Negawatt power
    Negawatt power

    Negawatt power is a term coined and introduced by Amory Lovins in a 1989 speech.This technique works by investing to reduce electricity demand instead of investing to increase electricity generation capacity....
  • Standby power
    Standby power

    Standby power, also called vampire power, phantom load, or leaking electricity, refers to the electric power consumed by electronic appliances while they are switched off or in a sleep mode....
  • Other measures of efficiency:
  • Thermal efficiency
    Thermal efficiency

    In thermodynamics, the thermal efficiency is a Dimensionless quantity performance measure of a thermal device such as an internal combustion engine, a boiler, or a furnace, for example....
  • Mechanical efficiency
    Mechanical efficiency

    In physics, mechanical efficiency is the effectiveness of a machine and is defined asMechanical Efficiency is the ratio of work input to work output....
  • Performance per watt
    Performance per watt

    In computing, performance per watt is a measure of the energy efficiency of a particular computer architecture or computer hardware. Literally, it measures the rate of computation that can be delivered by a computer for every watt of power consumed....
  • Efficiency improvement initiatives:
  • 80 plus
    80 PLUS

    80 PLUS is an initiative to promote more electrical energy efficiency Computer power supply . It certifies products that have more than 80% energy efficiency at 20%, 50% and 100% of rated load, and a power factor of 0.9 or greater at 100% load....
  • One watt initiative
    One Watt Initiative

    The One Watt Initiative is an energy saving proposal by the International Energy Agency to reduce standby power-use in all appliances to just one watt....
  • Energy star
    Energy Star

    Energy Star is an international standard for Energy conservation consumer products. It was first created as a United States government program in 1992, but Australia, Canada, Japan, New Zealand, Taiwan and the European Union have also adopted the program....


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